Method of manufacturing artificial aggregate for mortars and concretes



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METHOD OF MANUFACTURING ARTIFICIAL AGGREGATE FOR uoRTARs AND CONCRBTESFiled Feb. 16. 1929 //v VENTOP. JOHN 5. GREEN/i WA L7.

Patented Dec. 30; 1930 UNITED STATES PATENT OFFICE JOHN E. GREENAWALT,OF NEW YORK, N. Y.

METHOD OF MANUFACTURING ARTIFICIAL AGGREGATE FOR MORTARS AND CONCRETESApplication filed February 16, 1929. Serial No. 340,642.

, directed to the heat treatment of clay, preferably by sintering, toconvert the clay into a hard. porous, homogeneous product that isespecially suitable when crushed, for use as a concrete aggregate,either en masse or in blocks.

I am aware that clay has been heat treated in kilns and in heaps for thepurpose of forming a hard, inert substance having desirable propertiesas an aggregate; but such treatment is extremely wasteful in the amountof fuel required. I am also familiar with the efforts that have beenmade to sinter clay to produce a desirable building product. However, asfar as I know, the sintering, as heretofore attempted, consisted inmixing finely ground clay and fuel and moistening with water, in whichcondition the mixture was charged onto a downdraft sintering apparatusfor treatment. I have found that satisfactory results cannot be obtainedwith a mere mixture of fuel (such as powdered coke) and ground clay,owing to the tendency of the clay to pack and the moist particlesthereof to adhere, which closes the voids in the charge and prevents thefree passage of air therethrough. If sufficient fuel is used to preventpacking the temperature during the treatment becomes too high andresults in excessive fusion, as well as prohibitive cost of operation.

My invention contemplates the sintering of a charge made up of finelycrushed clay' and ordinary furnace cindc Tie proportion of from 20 ,0 oo 76 cinders. The cinders used contain all the original substance asthey come from the grate, that is ashes, clinkers, unburned coal andcoke, the coal and coke being present in suflicient quantity to furnishthe necessary fuel for sintering. These cinders are finely crushed andmixed with the crushed clay in the proportions mentioned, and the chargethus made up then moistened slightly with water. If desired, themoistening may be done while the cinders and clay are being mixed. Thischarge is then placed on a sintering apparatus of either theGreenawaltor Dwight & Lloyd type, care being taken not to compact thecharge as it is important that the voids therein be preserved.

In the drawings, a Greenawalt sintering apparatus is shown, the samecomprising a rotatable pan, 1, to the hollow trunnions 2, 2 of which isconnected a dust chamber 3 by means of conduits 4, 4. A suitableexhauster 5 serves to create suction in the chamber 3, and of coursethrough the pan, and has its outlet 6 connected to a stack 7. A chargecar 8 may be used to feed the material 727., m onto the grate 9 of thesintering pan, said material being preferably fed with the component mof the coarser particles directly onto the grate and the component m ofthe finer particles on the coarser particles. Thus the two components,after being placed in the pan 1, constitute the charge that is to hesintered.

An igniter 10 is now moved into position over the charge C and theexhauster 5 set into operation after which the fuel in the igniter iskindled to immediately fill the igniter with flame, which is sucked intothe charge by the action of the exhauster and ignites the combustiblestherein.

After ignition the combustion of the fuel contained in the cinderscontinues downwardl through the charge under the influence of theexhauster which causes a downward flow of air through the voids in thecharge.

The particles of clinker and ash in the charge not only preserve itsvoids and permit the passage of air therethrough, but also supply silicawhich fuses readily and unites with the expanded and partially fusedclay particles. Thus, at the completion of the sintering operation therehas resulted a cake or slab of substantially uniformly porous burntclay, the expanded particles of which are thoroughly fused together bythe fusible elements in the charge. This product is not only extremelylight of weight, (on account of its porosity) but is also remarkablystrong in structure. The slab of sintered clay,

after having cooled, is crushed to the proper size for the use to whichit is to be put. If concrete blocks are to be made both the fine and thecoarse particles are used in a mixture with cement in any desiredproportion, and molded into shape.

The terms sintering and sinter, as used herein, have substantially thesame meaning that they have in the metallurgical art: to wit, sinteringin the process of treating materials (generally metalliferous) bysubjecting a charge of finely crushed material containing a combustibleto the heat'generated by the internal combustion of said fuel supportedby a blast of air passing through the charge. Ignition is effected bythe momentary action of a flame at one surface of the charge, thecombustion being carried on through the charge under the influence ofthe air blast. A sinter is the hard, cellular or porous, product ofcomparative light wei ht produced by this sintering action.

The granular nature of crushed ore, and its non-plasticity when wetmakes it adaptable to the sintering process, while the ease with whichdry clay pulverizes and its plasticity when wet makes clay diificult tohandle. The present method of treatment overcomes these difiiculties.

Having described my invention I claim:

1. The process of manufacturing a concrete aggregate which comprisesmixing finely crushed clay and cinders, charging said mixture in asuitable vessel, passing a combustion supporting gas therethrough,igniting the charge at its surface, and continuing to pass thecombustion supporting gas through the charge until the same is sintered.

2. The process of manufacturing a concrete aggregate, which comprisesmixing finely crushed clay and cinders to form a charge, and sinteringsaid charge to form a hard cellular cake.

3. The process of manufacturing a concrete aggregate, which comprisesmixing finely crushed clay and cinders in the proportion of not lessthan 25% cinders, moistening said mixture, and sintering the same toform a hard cellular cake.

4. The process of manufacturing a concrete aggregate which comprisesmixing finely crushed clay and cinders, charging said mixture in asuitable vessel without pressure to preserve the voids therein, passinga combustion supporting gas thcrethrough, igniting the charge at itssurface, and continuing to pass the combustion supporting gas throughthe charge until the same is sintered.

In testimony whereof I hereunto afiix my signature.

JOHN E. GREENAWALT.

